Why do we try to enter U1 mode in SuperSpeed?

[Hans Petter Selasky]

On 03/30/15 10:54, Hans Petter Selasky wrote:
> On 03/30/15 06:54, Kohji Okuno wrote:
>> Hi HPS
>>
>> I have a question.
>> Why do we try to enter U1 mode in SuperSpeed?
>> This is the following codes(***)
>>
>> In our proprietary environmen(This has a xHCI controller), when a
>> device accept U1, the device may be strange status. Acutually, when I
>> tried to connect "Western Digital My Passport Essential 320GB
>> (P/N:WDBACY3200ABK-00)", this HDD was not recognized correctly.
>> But, in PC environment, this HDD was recognized correctly.
>>
>> Regards,
>>   Kohji Okuno
>>
>> (***)
>> usb_hub.c:
>> 793            if (speed == USB_SPEED_SUPER) {
>> 794                    err = usbd_req_set_hub_u1_timeout(udev, NULL,
>> 795                        portno, 128 - (2 * udev->depth));
>> 796                    if (err) {
>> 797                            DPRINTFN(0, "port %d U1 timeout "
>> 798                                "failed, error=%s\n",
>> 799                                portno, usbd_errstr(err));
>> 800                    }
>> 801                    err = usbd_req_set_hub_u2_timeout(udev, NULL,
>> 802                        portno, 128 - (2 * udev->depth));
>> 803                    if (err) {
>> 804                            DPRINTFN(0, "port %d U2 timeout "
>> 805                                "failed, error=%s\n",
>> 806                                portno, usbd_errstr(err));
>> 807                    }
>> 808            }
>
> Hi,
>
> We are not trying to enter U1 mode, we only setup the U1 and U2
> timeouts. Is there a flag in the USB descriptors that say this is not
> supported and that we need to set some other value? I thought all
> superspeed devices had to support these features and that switching in
> and out of the sleep modes was done by the XHCI hardware.
>
> --HPS
>

Hi,

Looking at the USB 3.0 specification, I think there might be a typo there:

In table 10-13 - "U2 timeout value encoding", it says that 0xFE 
corresponds to 65024 ms, but I think it should be 65024 _us_ !

Try programming values 0xFF for both U1 and U2. Does the device 
enumerate then?

Maybe it only doesn't support sleep modes during enumeration and that 
after set configuration it works?

--HPS